Specter

Specters are fast, high damage, high health non-elite mobs which will occasionally teleport behind players. Specters can't be knocked back. They will occasionally spawn when a player kills a mob in a dungeon delve with the spectral or dreadful modifier.

Spawning

In spectral delve instances, there is an invisible counter that increases by 2-5 points every time the player kills a mob. Once the counter is at a value greater than or equal to 20, a Specter is spawned and the counter is decreased by 20 points.

In dreadful delve instances, the counter instead increases by 2-4 for killing a normal mob, and by 4-7 points for killing an elite mob. A mob is spawned every 10 points instead of 20. Spawning a mob will also only decrease the counter by 10 points. If the mob that caused to counter to hit 10 or higher was normal mob, a Specter will be spawned. Otherwise, a Dreadnaught will spawn.